This study is designed to elucidate measures to increase the serviceable life of dental amalgam restorations. In this fifth year of the project five year old restorations are being observed for margin integrity, contour and surface texture. Concurrently, laboratory tests are being made and the data correlated with the clinical observations. The laboratory data include measurements of physical properties such as dimensional changes during hardening and over 2 and 3 years in varying storage temperatures. Some dimensional change specimens are unrestricted and others are in cavities. Unrestricted specimens have a wide range of dimensional changes which seem to be related to composition of the alloy and also time and temperature related phase changes. The same brands and batches of amalgams confined to cavities do not have expansions similar to the unrestricted specimens but are directly related to their individual creep values. The causes of this phenomenon are being studied by chemical, x-ray diffraction, metallographic and electron probe procedures. The results should give clues to further composition changes and techniques of manipulation which should improve amalgam restorations, and through these, to better dental health.